Outline

Question: To determine whether heart rate variability (HRV) can be related to echocardiographic measurements of cardiac dimension or function in hypertensive patients with a history of atrial fibrillation (AF).

Method Used: One hundred fifty five treated essential hypertensive patients in sinus rhythm, 77 with a documented history of AF and 78 without a history of AF were evaluated between 08:00 and 11:00 AM. The autonomic nervous system was assessed at rest in supine position for 20 min and during active standing for 10 min by R-R interval (NN) measurements and short-term (5min) heart rate variability (HRV) analysis. From the time series of normal NN the time domain variables were calculated: standard deviation of NN (SDNN) and the percentage of cycles differing from the preceding one by >50 ms (pNN50). Frequency domain parameters in absolute and normalized units were calculated for low-frequency power (LF), high-frequency power (HF) and the LF/HF ratio determined. A transthoracic two-dimensional and M-mode echocardiogram was performed to calculate left atrial (LA) volume, left ventricular (LV) mass index and LA and LV ejection fraction (EF).

Results: At rest and during standing, NN was significantly (p<0.05) longer and the LF component as well as the delta change of LF were significantly (p<0.05) lower in the hypertensive patients with a history of AF. LA volume was significantly (p<0.05) greater and atrial EF was significantly (p<0.05) reduced in patients with a history of AF. The reduction of the LF component was inversely related to LA enlargement and directly related to LA dysfunction. LV mass index and ventricular ejection fraction were not different between the two groups of patients.

Conclusion: Hypertensive patients with a history of AF have a lower heart rate and LF component of HRV, at rest and during standing, suggesting a decreased cardiac sympathetic responsiveness which is associated with LA enlargement and contractile dysfunction.